This project is concerned with the development of statistical/mathematical methodology useful in the assessment of human health risk associated with exposure to hazardous environmental agents. Special emphasis is given to the generation of improved statistical techniques for estimating potential human cancer risk from laboratory animal data. Current research efforts are particularly concerned with the role of pharmacokinetics in low-dose extrapolation modeling and with the estimation of lifetime cancer risk when the duration of exposure is less than a normal lifespan. Studies of the factors that influence species scale-up for non-carcinogenic endpoints like terata are also underway.